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In JoVE (1)
Other Publications (17)
- Lab on a Chip
- Biosensors & Bioelectronics
- Lab on a Chip
- Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
- The Journal of Investigative Dermatology
- Biomedical Microdevices
- PloS One
- Journal of Micromechanics and Microengineering : Structures, Devices, and Systems
- Biomedical Microdevices
- Physics in Medicine and Biology
- Journal of Cell Science
- Biochemical and Biophysical Research Communications
- Lab on a Chip
- Biosensors & Bioelectronics
- The Journal of Biological Chemistry
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Articles by Arum Han in JoVE
תא Multi-CNS-Neuron גליה שותף תרבות Microfluidic רציף
Jaewon Park1, Hisami Koito2, Jianrong Li2, Arum Han1
1Department of Electrical and Computer Engineering, Texas A&M University (TAMU), 2Department of Veterinary Integrative Biosciences, Texas A&M University (TAMU)
פיתחנו רומן רב תא שיתוף תרבות נוירון פלטפורמה עבור microsystem ב CNS מחקר במבחנה אינטראקציה האקסון, גליה. פלטפורמה המסוגלת לנהל עד שישה ניסויים עצמאיים במקביל היה מפוברק באמצעות פיתח מאקרו / מיקרו שיטת ייצור כלאיים.
Other articles by Arum Han on PubMed
Lab on a Chip. Aug, 2003 | Pubmed ID: 15100766
This paper describes an approach for fabricating multi-layer microfluidic systems from a combination of glass and plastic materials. Methods and characterization results for the microfabrication technologies underlying the process flow are presented. The approach is used to fabricate and characterize multi-layer plastic/glass microfluidic systems containing electrical and mechanical functionality. Hot embossing, heat staking of plastics, injection molding, microstenciling of electrodes, and stereolithography were combined with conventional MEMS fabrication techniques to realize the multi-layer systems. The approach enabled the integration of multiple plastic/glass materials into a single monolithic system, provided a solution for the integration of electrical functionality throughout the system, provided a mechanism for the inclusion of microactuators such as micropumps/valves, and provided an interconnect technology for interfacing fluids and electrical components between the micro system and the macro world.
Biosensors & Bioelectronics. Apr, 2006 | Pubmed ID: 16529922
This paper presents the development of a microsystem for separating suspended breast cancer cells in peripheral blood and for sorting them based on their electrophysiological characteristics. A continuous paramagnetic capture mode (PMC) magnetophoretic microseparator was utilized for the isolation of suspended breast cancer cells in peripheral blood based on the native magnetic properties of blood cells without any tagging such as with magnetic probes. A micro-electrical impedance spectroscopy (mu-EIS) system was used as a downstream cell analysis tool to extract the pathological characteristics from the breast cancer cells. The system was fabricated on silicon and glass substrates utilizing microfabrication and stereolithography technologies. The experimental results of the PMC microseparator show that 94.8% of the breast cancer cells could be continuously separated out from a spiked blood sample with a 0.2 T external magnetic flux. The electrical impedances of human breast cancer cell lines of different pathological stages (MCF-7, MDA-MB-231, and MDA-MB-435) were measured using mu-EIS and compared to those of normal human breast tissue cell line MCF-10A.
Lab on a Chip. Nov, 2006 | Pubmed ID: 17066163
A micro electrical impedance spectroscopy system (microEIS) for single cell analysis has been developed and used to differentiate ion channel activities of bovine chromaffin cells. K+ and Ca2+ channels were blocked and their electrical impedances were measured over a frequency range of 100 Hz to 5.0 MHz and compared to that of unblocked chromaffin cells. When ion channels were blocked, an increase in magnitude and decrease in phase of the measured impedances were observed. This result demonstrates that ion channel activities can be distinguished using the developed microsystem and it is expected that this system can be used to provide positive/negative information of ion channel blockage in a high throughput screening setup.
Quantification of the Heterogeneity in Breast Cancer Cell Lines Using Whole-cell Impedance Spectroscopy
Clinical Cancer Research : an Official Journal of the American Association for Cancer Research. Jan, 2007 | Pubmed ID: 17200348
Quantification of the heterogeneity of tumor cell populations is of interest for many diagnostic and therapeutic applications, including determining the cancerous stage of tumors. We attempted to differentiate human breast cancer cell lines from different pathologic stages and compare that with a normal human breast tissue cell line by characterizing the impedance properties of each cell line.
Blood. Aug, 2007 | Pubmed ID: 17400912
To define prognostic impact of Epstein-Barr virus (EBV) infection in diffuse large B-cell lymphoma (DLBCL), we investigated EBV status in patients with DLBCL. In all, 380 slides from paraffin-embedded tissue were available for analysis by EBV-encoded RNA-1 (EBER) in situ hybridization, and 34 cases (9.0%) were identified as EBER-positive. EBER positivity was significantly associated with age greater than 60 years (P = .005), more advanced stage (P < .001), more than one extranodal involvement (P = .009), higher International Prognostic Index (IPI) risk group (P = .015), presence of B symptom (P = .004), and poorer outcome to initial treatment (P = .006). The EBER(+) patients with DLBCL demonstrated substantially poorer overall survival (EBER(+) vs EBER(-) 35.8 months [95% confidence interval (CI), 0-114.1 months] vs not reached, P = .026) and progression-free survival (EBER(+) vs EBER(-) 12.8 months [95% CI, 0-31.8 months] vs 35.8 months [95% CI, 0-114.1 months], respectively (P = .018). In nongerminal center B-cell-like subtype, EBER in situ hybridization positivity retained its statistical significance at the multivariate level (P = .045). Nongerminal center B-cell-like patients with DLBCL with EBER positivity showed substantially poorer overall survival with 2.9-fold (95% CI, 1.1-8.1) risk for death. Taken together, DLBCL patients with EBER in situ hybridization+ pursued more rapidly deteriorating clinical course with poorer treatment response, survival, and progression-free survival.
Biomaterials. Aug, 2008 | Pubmed ID: 18455788
Poly(N-isopropylacrylamide) (PNIPAAm) hydrogels become more hydrophobic when they reversibly switch from a water-swollen to a deswollen state above the volume phase transition temperature (VPTT, approximately 33 degrees C) which has been used to modulate cell adhesion. In the current work, we prepared novel thermoresponsive nanocomposite hydrogels comprised of a PNIPAAm hydrogel matrix and polysiloxane colloidal nanoparticles ( approximately 220 nm average diameter) via in situ photopolymerization of aqueous solutions of NIPAAm monomer, N,N'-methylenebisacrylamide (BIS, crosslinker), photoinitiator and polysiloxane nanoparticles (0.5-2.0 wt% based on solution weight) at approximately 7 degrees C. The VPTT of the nanocomposite hydrogels is not altered versus the pure PNIPAAm hydrogel. Dynamic mechanical analysis and tensile tests revealed that higher nanoparticle content generally produced improved hydrogel mechanical properties. Surfaces of nanocomposite hydrogels became increasingly more hydrophobic at all temperatures between 10 and 40 degrees C as the amount of hydrophobic polysiloxane nanoparticles was increased. When cooled from 37 to 25 degrees C, mouse smooth muscle precursor cells (10T1/2) were effectively detached from nanocomposite hydrogel surfaces. The utility of photopatterning to create surface micropillars comprised of nanocomposite hydrogels was demonstrated.
Non-compensating Roles Between Nckalpha and Nckbeta in PDGF-BB Signaling to Promote Human Dermal Fibroblast Migration
The Journal of Investigative Dermatology. Aug, 2009 | Pubmed ID: 19242519
Platelet-derived growth factor BB (PDGF-BB) is a Food and Drug Administration (FDA)-approved growth factor, acting as a mitogen and motogen of dermal fibroblasts (DFs), for skin wound healing. The two closely related SH2/SH3 adapter proteins, Nckalpha and Nckbeta, connect PDGF-BB signaling to the actin cytoskeleton and cell motility. The mechanism has not been fully understood. In this study, we investigated, side by side, the roles of Nckalpha and Nckbeta in PDGF-BB-stimulated DF migration. We found that cells expressing the PDGFRbeta-Y751F mutant (preventing Nckalpha binding) or PDGFRbeta-Y1009F mutant (preventing Nckbeta binding), DF cells isolated from Nckalpha- or Nckbeta-knockout mice, and primary human DF cells with RNA interference (RNAi) knockdown of the endogenous Nckalpha or Nckbeta all failed to migrate in response to PDGF-BB. Overexpression of the middle SH3 domain of Nckalpha or Nckbeta alone in human DFs also blocked PDGF-BB-induced cell migration. However, neither Nckalpha nor Nckbeta was required for the activation of the PDGF receptor, p21-activated protein kinase (Pak1), AKT, extracellular signal-regulated kinase (ERK) 1/2, or p38MAP by PDGF-BB. Although PDGF-BB stimulated the membrane translocation of both Nckalpha and Nckbeta, Nckalpha appeared to mediate Cdc42 signaling for filopodium formation, whereas Nckbeta mediated Rho signaling to induce stress fibers. Thus, this study has elucidated the independent roles and mechanisms of action of Nckalpha and Nckbeta in DF migration, which is critical for wound healing.
Biomedical Microdevices. Dec, 2009 | Pubmed ID: 19554452
This paper presents a circular microfluidic compartmentalized co-culture platform that can be used for central nervous system (CNS) axon myelination research. The microfluidic platform is composed of a soma compartment and an axon/glia compartment connected through arrays of axon-guiding microchannels. Myelin-producing glia, oligodendrocytes (OLs), placed in the axon/glia compartment, interact with only axons but not with neuronal somata confined to the soma compartment, reminiscent to in vivo situation where many axon fibres are myelinated by OLs at distance away from neuronal cell bodies. Primary forebrain neurons from embryonic day 16-18 rats were cultured inside the soma compartment for two weeks to allow them to mature and form extensive axon networks. OL progenitors, isolated from postnatal day 1-2 rat brains, were then added to the axon/glia compartment and co-cultured with neurons for an additional two weeks. The microdevice showed fluidic isolation between the two compartments and successfully isolated neuronal cell bodies and dendrites from axons growing through the arrays of axon-guiding microchannels into the axon/glia compartment. The circular co-culture device developed here showed excellent cell loading characteristics where significant numbers of cells were positioned near the axon-guiding microchannels. This significantly increased the probability of axons crossing these microchannels as demonstrated by the more than 51 % of the area of the axon/glia compartment covered with axons two weeks after cell seeding. OL progenitors co-cultured with axons inside the axon/glia compartment successfully differentiated into mature OLs. These results indicate that this device can be used as an excellent in vitro co-culture platform for studying localized axon-glia interaction and signalling.
PloS One. 2009 | Pubmed ID: 19668333
Microbial fuel cells (MFCs) are remarkable "green energy" devices that exploit microbes to generate electricity from organic compounds. MFC devices currently being used and studied do not generate sufficient power to support widespread and cost-effective applications. Hence, research has focused on strategies to enhance the power output of the MFC devices, including exploring more electrochemically active microbes to expand the few already known electricigen families. However, most of the MFC devices are not compatible with high throughput screening for finding microbes with higher electricity generation capabilities. Here, we describe the development of a microfabricated MFC array, a compact and user-friendly platform for the identification and characterization of electrochemically active microbes. The MFC array consists of 24 integrated anode and cathode chambers, which function as 24 independent miniature MFCs and support direct and parallel comparisons of microbial electrochemical activities. The electricity generation profiles of spatially distinct MFC chambers on the array loaded with Shewanella oneidensis MR-1 differed by less than 8%. A screen of environmental microbes using the array identified an isolate that was related to Shewanella putrefaciens IR-1 and Shewanella sp. MR-7, and displayed 2.3-fold higher power output than the S. oneidensis MR-1 reference strain. Therefore, the utility of the MFC array was demonstrated.
Micropatterning of Poly(dimethylsiloxane) Using a Photoresist Lift-off Technique for Selective Electrical Insulation of Microelectrode Arrays
Journal of Micromechanics and Microengineering : Structures, Devices, and Systems. May, 2009 | Pubmed ID: 19946385
A poly(dimethylsiloxane) (PDMS) patterning method based on a photoresist lift-off technique to make an electrical insulation layer with selective openings is presented. The method enables creating PDMS patterns with small features and various thicknesses without any limitation in the designs and without the need for complicated processes or expensive equipments. Patterned PDMS layers were created by spin-coating liquid phase PDMS on top of a substrate having sacrificial photoresist patterns, followed by a photoresist lift-off process. The thickness of the patterned PDMS layers could be accurately controlled (6.5-24 µm) by adjusting processing parameters such as PDMS spin-coating speeds, PDMS dilution ratios, and sacrificial photoresist thicknesses. PDMS features as small as 15 µm were successfully patterned and the effects of each processing parameter on the final patterns were investigated. Electrical resistance tests between adjacent electrodes with and without the insulation layer showed that the patterned PDMS layer functions properly as an electrical insulation layer. Biocompatibility of the patterned PDMS layer was confirmed by culturing primary neuron cells on top of the layer for up to two weeks. An extensive neuronal network was successfully formed, showing that this PDMS patterning method can be applied to various biosensing microdevices. The utility of this fabrication method was further demonstrated by successfully creating a patterned electrical insulation layer on flexible substrates containing multi-electrode arrays.
Biomedical Microdevices. Apr, 2010 | Pubmed ID: 20049640
We present a novel micro-macro hybrid soft-lithography master (MMHSM) fabrication technique where microdevices having both microscale and macroscale features can be replicated with a single soft-lithography step. A poly(methyl methacrylate) (PMMA) master having macroscale structures was first created by a bench-top milling machine. An imprinting master mold having microscale structures was then imprinted on the PMMA surface through a hot-embossing process to obtain a PMMA master mold. A poly(dimethylsiloxane) (PDMS) master was then replicated from this PMMA master through a standard soft-lithography process. This process allowed both microscale (height: 3-20 microm, width: 20-500 microm) and macroscale (height: 3.5 mm, width: 1.2-7 mm) structures to co-exist on the PDMS master mold, from which final PDMS devices could be easily stamped out in large quantities. Microfluidic structures requiring macroscale dimensions in height, such as reservoirs or fluidic tubing interconnects, could be directly built into PDMS microfluidic devices without the typically used manual punching process. This significantly reduced alignment errors and time required for such manual fabrication steps. In this paper, we successfully demonstrated the utility of this novel hybrid fabrication method by fabricating a PDMS microfluidic device with 40 built-in fluidic interfaces and a PDMS multi-compartment neuron co-culture platform, where millimeter-scale compartments are connected via arrays of 20 microm wide and 200 microm long microfluidic channels. The resulting structures were characterized for the integrity of the transferred pattern sizes and the surface roughness using scanning electron microscopy and optical profilometry.
Physics in Medicine and Biology. Aug, 2010 | Pubmed ID: 20679698
Ultrasound is emerging as an attractive alternative modality to standard x-ray and CT methods for bone assessment applications. As of today, however, there is a lack of systematic studies that investigate the performance of diagnostic ultrasound techniques in bone imaging applications. This study aims at understanding the performance limitations of new ultrasound techniques for imaging bones in controlled experiments in vitro. Experiments are performed on samples of mammalian and non-mammalian bones with controlled defects with size ranging from 400 microm to 5 mm. Ultrasound findings are statistically compared with those obtained from the same samples using standard x-ray imaging modalities and optical microscopy. The results of this study demonstrate that it is feasible to use diagnostic ultrasound imaging techniques to assess sub-millimeter bone defects in real time and with high accuracy and precision. These results also demonstrate that ultrasound imaging techniques perform comparably better than x-ray imaging and optical imaging methods, in the assessment of a wide range of controlled defects both in mammalian and non-mammalian bones. In the future, ultrasound imaging techniques might provide a cost-effective, real-time, safe and portable diagnostic tool for bone imaging applications.
TbetaRI/Alk5-independent TbetaRII Signaling to ERK1/2 in Human Skin Cells According to Distinct Levels of TbetaRII Expression
Journal of Cell Science. Jan, 2011 | Pubmed ID: 21172820
TGFβ binding to the TGFβ receptor (TβR) activates R-Smad-dependent pathways, such as Smad2/3, and R-Smad-independent pathways, such as ERK1/2. The mechanism of the TGFβ-TβRII-TβRI-Smad2/3 pathway is established; however, it is not known how TGFβ activates ERK1/2. We show here that although TGFβ equally activated Smad2/3 in all cells, it selectively activated ERK1/2 in dermal cells and inhibited ERK1/2 in epidermal cells. These opposite effects correlated with the distinct expression levels of TβRII, which are 7- to 18-fold higher in dermal cells than in epidermal cells. Reduction of TβRII expression in dermal cells abolished TGFβ-stimulated ERK1/2 activation. Upregulation of TβRII expression in epidermal cells to a similar level as that in dermal cells switched TGFβ-induced ERK1/2 inhibition to ERK1/2 activation. More intriguingly, in contrast to the equal importance of TβRII in mediating TGFβ signaling to both Smad2/3 and ERK1/2, knockdown of TβRI/Alk5 blocked activation of only Smad2/3, not ERK1/2, in dermal cells. Similarly, expression of the constitutively activated TβRI-TD kinase activated only Smad2/3 and not ERK1/2 in epidermal cells. This study provides an explanation for why TGFβ selectively activates ERK1/2 in certain cell types and direct evidence for TβRI-independent TβRII signaling to a R-Smad-independent pathway.
Crystal Structure of Bifunctional 5,10-methylenetetrahydrofolate Dehydrogenase/cyclohydrolase from Thermoplasma Acidophilum
Biochemical and Biophysical Research Communications. Mar, 2011 | Pubmed ID: 21333632
Folate co-enzymes play a pivotal role in one-carbon transfer cellular processes. Many eukaryotes encode the tri-functional tetrahydrofolate dehydrogenase/cyclohydrolase/synthetase (deh/cyc/syn) enzyme, which consists of a N-terminal bifunctional domain (deh/cyc) and a C-terminal monofunctional domain (syn). Here, we report the first analogous archeal enzyme structures, for the bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase from Thermoplasma acidophilum (TaMTHFDC) as the native protein and also as its NADP complex. The TaMTHFDC structure is a dimer with a polar interface, as well as a NADP binding site that shows minor conformational change. The orientations of the residues in the NADP binding site do not change on ligand binding, incorporating three water molecules which are hydrogen bonded with phosphate groups of NADP in the structure of the complex. Our structural information will contribute to an improved understanding of the basis of THF and one-carbon metabolism.
Lab on a Chip. Jul, 2011 | Pubmed ID: 21603723
We present the development of a microfluidically cryo-cooled planar coil for magnetic resonance (MR) microscopy. Cryogenically cooling radiofrequency (RF) coils for magnetic resonance imaging (MRI) can improve the signal to noise ratio (SNR) of the experiment. Conventional cryostats typically use a vacuum gap to keep samples to be imaged, especially biological samples, at or near room temperature during cryo-cooling. This limits how close a cryo-cooled coil can be placed to the sample. At the same time, a small coil-to-sample distance significantly improves the MR imaging capability due to the limited imaging depth of planar MR microcoils. These two conflicting requirements pose challenges to the use of cryo-cooling in MR microcoils. The use of a microfluidic based cryostat for localized cryo-cooling of MR microcoils is a step towards eliminating these constraints. The system presented here consists of planar receive-only coils with integrated cryo-cooling microfluidic channels underneath, and an imaging surface on top of the planar coils separated by a thin nitrogen gas gap. Polymer microfluidic channel structures fabricated through soft lithography processes were used to flow liquid nitrogen under the coils in order to cryo-cool the planar coils to liquid nitrogen temperature (-196 °C). Two unique features of the cryo-cooling system minimize the distance between the coil and the sample: (1) the small dimension of the polymer microfluidic channel enables localized cooling of the planar coils, while minimizing thermal effects on the nearby imaging surface. (2) The imaging surface is separated from the cryo-cooled planar coil by a thin gap through which nitrogen gas flows to thermally insulate the imaging surface, keeping it above 0 °C and preventing potential damage to biological samples. The localized cooling effect was validated by simulations, bench testing, and MR imaging experiments. Using this cryo-cooled planar coil system inside a 4.7 Tesla MR system resulted in an average image SNR enhancement of 1.47 ± 0.11 times relative to similar room-temperature coils.
Air-cathode Microbial Fuel Cell Array: a Device for Identifying and Characterizing Electrochemically Active Microbes
Biosensors & Bioelectronics. Jan, 2011 | Pubmed ID: 20655725
Microbial fuel cells (MFCs) have generated excitement in environmental and bioenergy communities due to their potential for coupling wastewater treatment with energy generation and powering diverse devices. The pursuit of strategies such as improving microbial cultivation practices and optimizing MFC devices has increased power generating capacities of MFCs. However, surprisingly few microbial species with electrochemical activity in MFCs have been identified because current devices do not support parallel analyses or high throughput screening. We have recently demonstrated the feasibility of using advanced microfabrication methods to fabricate an MFC microarray. Here, we extend these studies by demonstrating a microfabricated air-cathode MFC array system. The system contains 24 individual air-cathode MFCs integrated onto a single chip. The device enables the direct and parallel comparison of different microbes loaded onto the array. Environmental samples were used to validate the utility of the air-cathode MFC array system and two previously identified isolates, 7Ca (Shewanella sp.) and 3C (Arthrobacter sp.), were shown to display enhanced electrochemical activities of 2.69 mW/m(2) and 1.86 mW/m(2), respectively. Experiments using a large scale conventional air-cathode MFC validated these findings. The parallel air-cathode MFC array system demonstrated here is expected to promote and accelerate the discovery and characterization of electrochemically active microbes.
β-CATENIN/CBP-DEPENDENT REGULATION OF TGF-β-MEDIATED EPITHELIAL-MESENCHYMAL TRANSITION (EMT) BY SMAD3
The Journal of Biological Chemistry. Jan, 2012 | Pubmed ID: 22241478
Interactions between transforming growth factor-β(TGF-β]) and Wnt are crucial to many biological processes, although specific targets, rationale for divergent outcomes (differentiation vs block of epithelial proliferation vs epithelial-mesenchymal transition (EMT)) and precise mechanisms in many cases remain unknown. We investigated β-catenin-dependent and transforming growth factor-β1 (TGF-β1) interactions in pulmonary alveolar epithelial cells (AEC) in the context of EMT and pulmonary fibrosis. We previously demonstrated that ICG-001, a small molecule specific inhibitor of the β-catenin/CBP (but not β-catenin/p300) interaction, ameliorates and reverses pulmonary fibrosis and inhibits TGF-β1-mediated α-smooth muscle actin (α-SMA) and collagen induction in AEC. We now demonstrate that TGF-β1 induces LEF/TCF TOPFLASH reporter activation and nuclear β-catenin accumulation, while LiCl augments TGF-β-induced α-SMA expression, further confirming co-operation between β-catenin- and TGF-β-dependent signaling pathways. Inhibition and knockdown of Smad3, knockdown of β-catenin and overexpression of ICAT abrogated effects of TGF-β1 on α-SMA transcription/expression, indicating a requirement for β-catenin in these Smad3-dependent effects. Following TGF-β treatment, co-immunoprecipitation demonstrated direct interaction between endogenous Smad3 and β-catenin, while chromatin immunoprecipitation (ChIP)-re-ChIP identified spatial and temporal regulation of α-SMA via complex formation among Smad3, β-catenin and CBP. ICG-001 inhibited α-SMA expression/transcription in response to TGF-β as well as α-SMA promoter occupancy by β-catenin and CBP, demonstrating a previously unknown requisite TGF-β1/β-catenin/CBP-mediated pro-EMT signaling pathway. Clinical relevance was shown by β-catenin/Smad3 co-localization and CBP expression in AEC of IPF patients. These findings suggest a new therapeutic approach to pulmonary fibrosis by specifically uncoupling CBP/catenin-dependent signaling downstream of TGF-β.